fix(module:select): arrow icon can be used when not using single-select

[DepickereSven]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: #5575

What is the new behavior?

That you can use the arrow icon in multi-select and tag mode.
But by default it's false. So you need to set it true in multi and tag mode.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[codecov]

Codecov Report

Merging #5785 into master will decrease coverage by 0.21%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5785      +/-   ##
==========================================
- Coverage   90.31%   90.09%   -0.22%     
==========================================
  Files         455      455              
  Lines       13788    13857      +69     
  Branches     2258     2185      -73     
==========================================
+ Hits        12452    12484      +32     
- Misses        819      849      +30     
- Partials      517      524       +7     

Impacted Files	Coverage Δ
components/select/select.component.ts	87.67% <100.00%> (+0.17%)	⬆️
components/tabs/tab-link.directive.ts	37.50% <0.00%> (-62.50%)	⬇️
components/tabs/tabset.component.ts	86.20% <0.00%> (-10.21%)	⬇️
components/carousel/strategies/base-strategy.ts	83.33% <0.00%> (-7.58%)	⬇️
components/tabs/tabs-ink-bar.directive.ts	83.87% <0.00%> (-3.23%)	⬇️
components/tabs/tab-nav-operation.component.ts	59.37% <0.00%> (-2.70%)	⬇️
components/i18n/date-helper.service.ts	85.00% <0.00%> (-2.50%)	⬇️
components/tabs/tab-nav-bar.component.ts	82.33% <0.00%> (-2.48%)	⬇️
components/breadcrumb/breadcrumb.component.ts	97.87% <0.00%> (-2.13%)	⬇️
components/table/src/table-style.service.ts	94.82% <0.00%> (-1.73%)	⬇️
... and 57 more

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[vthinkxie]

LGTM
thanks for your PR!

[github-actions]

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